Prior art control, as found on many applications of internal combustion engines, of engine valves is by means of timing cams positioned on a timing cam shaft which is operatively connected to the engine. Since this is a mechanical control and the cams are fixed, variations in timing of the operation of the valves is not possible.
Other prior art control is by means of controlling the flow of hydraulic fluid to and from solenoid valves which are aligned with the valve stems. One example of such a system is in U.S. Pat. No. 4,61 5,308 assigned to a common assignee by Wakeman, and entitled "Engine Valve Timing Control System". This form of control will allow a change in either the opening or the closing of the engine valve, but since the prime mover is still a cam, large variations in operational timing are not available to the engine performance designer.
U.S. Pat. No. 5,598,814, issued on Feb. 4, 1997, entitled "Method and Apparatus for Electrically Driving Engine Valves", describes a motor control including position transducers for generating crankshaft position and motor position pulse trains. The pulse trains are compared to detect any phase difference between engine and motor positions. Tables are generated to define the desired phase difference needed for particular valve characteristics. The phase difference represents the instantaneous deviation from the basic profile. One of the tables is selected according to the engine conditions and the motor is driven to achieve the desired phase differences.